IMS-VT: Don't send resume request when call changes.

When primary call changes VideoPauseController
triggers video resume request which fails since
the call was not paused before. This results in
displaying error notification on InCallUI.

Note that it is possible that video was paused
by remote UE so local UE shall not attempt to
resume the video by relying on the pause flag
only.

Change-Id: Id1d6411c6994312fe0019bf8da82262a50604633